Wind Power Plant

ABSTRACT

The invention relates to a wind power plant, comprising a rotor that can be rotated about a vertical axis, said rotor between two horizontal bearing planes disposed at a distance on top of each other comprising a plurality of rotor blades, which are disposed distributed on a circumferential circle, can each be pivoted about a vertical pivot axis, and the pivot range of which is delimited on both sides by a stop. In such a wind power plant, an improvement in the energy yield, while simultaneously ensuring another operation, is enabled in that the width of the rotor blades is smaller than approximately ⅓ the radius of the circumferential circle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/811,133, filed Jun. 29, 2010, which is the United States nationalphase of International Application No. PCT/CH2008/000549, filed Dec. 24,2008, which claims the benefit of Swiss Patent Application No. CH 8/08,filed Jan. 4, 2008. The disclosure of each of these documents is herebyincorporated in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to the field of alternative energyproduction by means of wind power.

2. Description of Related Art

Wind power installations, that is to say installations for obtaining(electrical) energy from the wind, have been known for a long time inwidely differing forms and embodiments. One fundamental distinguishingfeature between such wind power installations, which normally have arotor which rotates about a rotation axis, is the spatial arrangement ofthe rotation axis: in the case of so-called vertical rotors, the rotorrotates about a vertical axis, while in the case of horizontal rotors,the rotor rotates about a horizontal rotation axis. Vertical rotors,which also include the wind power installation according to the presentinvention, have the particular advantage over horizontal rotors thatthey do not need to be adjusted for a specific wind direction.

In principle, the power contained in the wind at a wind speed v isproportional to the cube of the wind speed v. The power extracted by thewind power installation increasingly reduces the wind speed. In theextreme (v→0), the power extracted tends to 0, because there is nolonger any flow through the rotor. There is therefore a maximum possiblepower that can be extracted, which is about 60% of the power containedin the wind.

The power which can be extracted from the wind is governed in particularby the nature of the rotor: the rotors of wind power installations areequipped with rotor blades on which two types of forces can act in thewind flow, specifically a force in the flow direction caused by the dragof the rotor blade and a lift force which acts transversely with respectto the flow direction, for example as is used in the case of aircraftwings.

The present invention relates to wind power installations which arebased mainly or exclusively on the drag (drag rotors). They aredistinguished by a high rotor torque which is available even duringstarting. WO A2-2005/046638 discloses a wind power installation which isin the form of a vertical rotor based on the drag principle and can havea number of stages in height. This wind power installation has thedisadvantage that a comparatively small number of broad rotor blades areused, which can be pivoted only in a very restricted pivoting range ofabout 45° about their pivoting axis. In consequence, the energy obtainedis not optimal. At the same time, its structure is considerably loadedby the pivoting movements and must be designed to be particularlyrobust.

JP-A-2005188494 discloses a wind power installation which is in the formof a vertical rotor based on the drag principle or the lift principleand whose rotor blades admittedly have a pivoting range of up to 180°,but whose rotor blades are so broad that only a small number (four orsix) can be arranged on the circumferential circle which is provided forthe pivoting axes. In this case as well, the yield is not optimal, andthe rotor running is particularly rough, and subject to largedisturbance forces.

SUMMARY OF THE INVENTION

The object of the invention is therefore to design a wind powerinstallation of the type mentioned initially which avoids thedisadvantages of known installations and results in more energy beingobtained while at the same time decreasing the mechanical load on thestructure. In one embodiment, the width of the rotor blades is chosen tobe small, and is less than approximately ⅓ of the radius of thecircumferential circle. The narrow rotor blades result in variousadvantages:

-   -   More rotor blades with a comparatively large pivoting range can        be arranged on the circumferential circle, which more        effectively convert, and therefore utilize, the wind flow        passing through the rotor volume to torque.    -   The load on the individual rotor blades is less, as a result of        which they can pivot more easily to the optimum position, and        produce reduced disturbance forces during pivoting and when        striking the limit stops of the pivoting range.    -   If the wind pressure on the rotor blades is not reduced by        reducing the width, the rotor blades can be made longer (in the        vertical direction) in order to achieve the same rotor area. The        torque is thus increased in comparison to broad rotor blades,        because the blade area is located further outward, overall.    -   The pivoting processes of the rotor blades are distributed        between considerably more pivoting axes on the circumferential        circle, which leads to smoother running of the rotor and to a        reduced load on the bearings and on the load-bearing structure.

One preferred refinement of the invention is distinguished in thattwelve or more rotor blades are arranged such that they can pivot on thecircumferential circle of the rotor.

The installation design is particularly simple if the rotor blades arein this case in the form of straight blades. Dispensing with an airfoilprofile or the like for the rotor blades considerably simplifiesproduction, and thus reduces the production costs.

If, according to another refinement, the rotor blades each have aleading edge and a trailing edge, and have a reduced thickness betweenthe leading edge and the trailing edge, the weight of the rotor bladesand the magnitude of the disturbance forces produced by them can befurther reduced without adversely affecting robustness.

If, on the other hand, the rotor blades have an aerodynamiccross-sectional profile, preferably in the form of a stretched droplet,with a pointed end and a round end, the rotor blades encounter less dragin the wind during their movement against the wind, thus increasing theoverall power yield of the installation.

The pivoting range of the rotor blades is preferably in each caselimited to an angle of about 100°. This allows optimum matching of therotor blades to the respective rotor position without any excessiveforces occurring on striking the limit points of the pivoting range.

It is particularly advantageous when, according to another refinement ofthe invention, in one limit position of the pivoting range, the rotorblades each include an angle of about 50° with the radius vector of thecircumferential circle which passes through the pivoting axis, and, inthe other limit position of the pivoting range, include an angle ofabout 150-165°.

One simple option for defining the pivoting range consists in that thepivoting axes of the rotor blades are arranged within the rotor blades,in the vicinity of, but at a distance from, the leading edge, and inthat the pivoting range of the rotor blades is in each case defined by asingle stop which is arranged within the circumferential circle.

However, it is also feasible for the pivoting axes of the rotor bladesto be arranged in the leading edges of the rotor blades, and for thepivoting range of the rotor blades to be defined in each case by alimiting element which is in the form of a circular arc, concentricallysurrounds the pivoting axis, and whose ends each form a stop.

If the aim is to design the installation to be particularly lightweight,it is advantageous for the mounting planes to be formed by spoked wheelswhich rotate about the axis.

In order to ensure that the wind pressure on the individual rotor bladesdoes not become excessive, it is expedient for the wind powerinstallation to have a plurality of rotors which are arranged atdifferent heights. This can be done without consuming a relatively largearea, by arranging the rotors one above the other, and by them rotatingabout the same axis.

In particular, in this case, different wind speeds can be utilizedbetter at different heights, if the rotors can rotate independently ofone another.

If the rotor blades have an aerodynamic cross-sectional profile,preferably in the form of a stretched droplet, with a pointed end and around end, it is advantageous for the pivoting axes of the rotor bladesto be arranged within the rotor blades in the vicinity of, but at adistance from, the round end, and for the pivoting range of the rotorblades each to be defined by a single stop which is arranged within therotor blade, rotationally fixed with respect to the pivoting axis.

The power can be tapped off in a particularly simple and advantageousmanner if the rotor drives at least one compressor via a powertransmission, which compressor sucks in air on the input side and isconnected on the output side to a compressed-air reservoir, and in thata turbine can be connected to the compressed-air reservoir and drives agenerator in order to produce electricity.

For better matching to different wind strengths, it is advantageous ifthe rotor can be selectively connected to a plurality of compressors viapower transmission. When the wind strength rises, compressors can beadditionally connected in order to process the additional power, andvice versa.

The wind power installation is particularly compact if thecompressed-air reservoir is incorporated in the ground, and forms thefoundation of the wind power installation arranged above it.

DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail in the following textwith reference to exemplary embodiments and in conjunction with thedrawing, in which:

FIG. 1 shows a highly simplified schematic illustration of a wind powerinstallation in the form of a vertical rotor, based on the dragprinciple, with two rotors one above the other, as is suitable forimplementation of the invention;

FIG. 2 shows a plan view from above of the rotor of a wind powerinstallation according to one exemplary embodiment of the invention;

FIG. 3 shows an illustration, comparable to FIG. 2, of a detail of therotor of a wind power installation according to another exemplaryembodiment of the invention;

FIG. 4 uses various sub-figures 4(a) to 4(c) to show various positionsof a rotor blade in the rotor as shown in FIG. 3;

FIG. 5 shows the variables which occur in a rotor as shown in FIG. 2;

FIG. 6 shows, in detail, the design of a rotor as shown in FIG. 2 with aspoked wheel for the rotor blades to be mounted on, according to anotherexemplary embodiment of the invention, with the rotor blade located atone end of the pivoting range;

FIG. 7 shows the rotor shown in FIG. 6 with the rotor blade at the otherend of the pivoting range;

FIG. 8 uses an illustration comparable to FIG. 2 to show a rotor withaerodynamically shaped rotor blades and angle ranges extended in thisway;

FIG. 9 shows an enlarged individual illustration of a rotor blade fromFIG. 8;

FIG. 10 shows the side view (FIG. 10 a) and an axial viewing directionof a wind power installation according to another exemplary embodimentof the invention with compressed-air storage; and

FIG. 11 shows a highly simplified installation layout for theinstallation shown in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a highly simplified schematic illustration of a wind powerinstallation in the form of a vertical rotor based on the drag principleand having two rotors one above the other, as is suitable forimplementation of the invention. The wind power installation 10 has avertical axis 11 about which two rotors 12 and 12′ rotate. Furtherrotors may, of course, also be provided, which rotate about the axis 11.However, it is just as possible to provide only a single rotor 12. Therotor or rotors 12, 12′ is or are connected via a shaft 16 to agenerator unit 17, which can also contain a gearbox in order to changethe rotation speed. Instead of the shaft 16, a shaft train comprising aplurality of individual shafts located concentrically one inside theother can be provided, via which the individual rotors 12, 12′ arecoupled to the generator unit 17 independently of their rotation. Thisis particularly advantageous when the aim is to optimally tap off flowstrata with different wind speeds by means of rotors 12, 12′ located atdifferent heights.

Each of the rotors 12, 12′ is equipped with a plurality of verticallyarranged rotor blades 15 which are mounted in a distributed manner, suchthat they can pivot, on a circumferential circle between a lowermounting plane 14 and an upper mounting plane 13. For the sake ofsimplicity and clarity, only the front rotor blades are in each caseshown in FIG. 1. FIG. 2 shows a plan view from above of a rotor 12according to one preferred exemplary embodiment of the invention,showing the interaction of the rotor 12 and of the rotor blades 15accommodated therein, with an air flow (wind) 20. The upper mountingplane 13 is in this case omitted in order to allow the rotor blades 15to be seen without any impediment. Overall, twelve rotor blades 15 arearranged distributed uniformly on the circumferential circle 27 and caneach pivot about a vertical pivoting axis 18. The pivoting range of eachrotor 15, which is shown in detail in FIGS. 5 and comprises an angle βof about 100° to 115°, is in each case bounded by a single stop 19 whichis in the form of a post and is placed a short distance away from thepivoting axis 18 within the circumferential circle 27.

Each rotor blade 15 is straight and has a leading edge 25 and a trailingedge 26 (FIG. 7). The pivoting axes 18 of the rotor blades 15 arearranged within the rotor blades 15, in the vicinity of, but at adistance from, the leading edge 25. At one limit position of thepivoting range (FIG. 6), that section of the rotor blade which islocated between the pivoting axis 18 and the leading edge 25 pivotsagainst the stop 19. In the other limit position (FIG. 7), that sectionof the rotor blade 15 which is located between the pivoting axis 18 andthe trailing edge 26 pivots against the stop 19. As can be seen fromFIG. 5, in one limit position of the pivoting range (β), the rotorblades 15 each include an angle α of about 50° with the radius vector ofthe circumferential circle 27 which passes through the pivoting axis 18,and in the other limit position of the pivoting range (β), include anangle 180°-γ of about 150° to 165°.

In another refinement, which is shown by way of example in FIGS. 3 and4, the pivoting axes 18 of the rotor blades 15 are arranged directly inthe leading edges 25 of the rotor blades 15. In this case, the pivotingrange (β) of the rotor blades 15 is in each case defined by a limitingelement 21 which is in the form of a circular arc and concentricallysurrounds the pivoting axis 18, and whose ends each form a stop 22 and23.

The comparatively narrow width b of the individual rotor blades 15 isessential for the invention (FIG. 5). The width b is less thanapproximately ⅓ of the radius R of the circumferential circle 27. Thisallows a comparatively large number of rotor blades 15 to beaccommodated on the circumferential circle 27 without having to limitthe pivoting range to do so. The interaction of the rotor 12 and of therotor blades 15 with the air flow is thus subdivided to a greaterextent, thus leading to better utilization in the volume, and tosmoother running.

The size and position of the pivoting range of the rotor blades as shownin FIG. 5 are also important. When the rotor 12 is revolving in theclockwise direction as shown in FIG. 2 and with the wind direction shownthere, this results in changing rotor blade positions, which can besubdivided into and associated with different angle ranges A to D: in afirst angle range A, which can be referred to as the drive range, therotor blades 15 rest on the stop 19 and are positioned transversely withrespect to the air flow 20, thus resulting in a driving torque. In theangle range B, the situation with respect to the position of the rotorblade 15 is unstable, because this is where the blade starts to separatefrom the stop 19. In the angle range C, the rotor blade 15 pivotsoutward and strikes against the stop 19 from the other side. Once again,this results in a driving torque. Because of the effect of the air flow20, a driving torque is also applied in an additional drive range (anglerange D) as a result of the chosen position of the pivoting range (seealso FIGS. 4 a and 4 b) until, later, the rotor blade is separated fromthe stop 19 and is positioned parallel to the air flow (right-hand sideof FIG. 2 and FIG. 3) in order to enter the angle range A again evenlater (see also FIG. 4 c).

The energy in the air flow 20 is utilized optimally by the position andsize of the pivoting range of the rotor blades. The splitting of thetotal rotor blade area between a multiplicity of comparatively narrowrotor blades 15 also contributes to this. This splitting at the sametime results in the rotor 12 running smoothly, reducing the magnitude ofthe disturbance forces associated with the pivoting. A furtherimprovement can be achieved if the thickness d of the rotor blades 15 isreduced in a center area 24 between the leading edge 25 and the trailingedge 26 (FIG. 6). In addition to the weight saved in each rotor blade 15by this measure, further weight can be saved, without any loss ofstrength, by forming the mounting planes 13, 14 by spoked wheels 28which rotate about the axis 11 (FIG. 6).

However, instead of the rotor blades 15 shown in FIGS. 6 and 7, it isalso possible to use aerodynamically optimized rotor blades 15′ as shownin FIG. 9, which are distinguished by a cross-sectional profile in theform of a stretched droplet with a pointed end 29 and a round end 30. Inthis case, the pivoting axis 18 is arranged at the round end 30. A stop31 is mounted in a rotationally fixed manner within the rotor blade 15′and has two stop surfaces 32 and 32′ which are oriented at an acuteangle to one another. In one limit position of the pivoting range (asshown in FIG. 9), one inner face of the rotor blade 15′ rests on thelower stop surface 32. In the other limit position, when the rotor blade15′ has been pivoted about the pivoting axis 18 in the counterclockwisedirection, the other inner face of the rotor blade 15′ rests on theupper stop surface 32′. The internal arrangement protects the stopmechanism against external influences such as icing, dirt or damage, andat the same time improves the aerodynamics. When rotor blades 15′ suchas these and as shown in FIG. 8 are installed in the rotor 12, thisresults in angle ranges A and D which are larger than those shown inFIG. 2.

Since the wind does not blow uniformly and continuously at many siteswhere wind power installations are installed, it is advantageous foroperational reasons to be able to store the energy that is producedeasily and effectively, and to withdraw the energy from the storageagain as required. The described rotor, which emits a high torque fromthe start as a drag rotor, is particularly highly suitable for operationof one or more compressors. When the compressors are used to suck in airand compress it, the compressed air that is produced can be stored in acompressed-air reservoir, and can drive a turbine or a compressed-airmotor, which produces electricity via a flange-connected generator, asrequired. A wind power installation such as this according to theinvention with a compressed-air reservoir is illustrated in the form ofthe preferred physical embodiment in FIG. 10, and in the form of ahighly simplified installation layout in FIG. 11.

25

In the case of the wind power installation 33 shown in FIG. 10, acompressed-air reservoir 40 in the form of a container, composed ofconcrete by way of example, is introduced into the ground. Thecompressed-air reservoir at the same time acts as a foundation for thewind power installation built above it. Three rotors or cells 35 a, 35 band 35 c are arranged one above the other on a mast 45 with a verticalcentral axis 34 and are designed, for example, as shown in FIG. 8. Themast 45 is anchored in a frame 37 which is built on the foundation, andis stabilized via a side guy 36. Power transmission 38, which isconnected to the rotors 35 a, b, c, and is in the form of a wheel orturntable is arranged within the frame 37, via which power transmission38 compressors 39 which are distributed on the circumference can bedriven in a manner which allows them to be connected selectively.

In the highly simplified installation layout shown in FIG. 11, the rotor35 drives a compressor 39 via the power transmission 38, whichcompressor 39 sucks in air at the inlet, compresses it and emits it atthe outlet via a first controllable valve 43 to the compressed-airreservoir 40. When it is intended to produce electrical energy,compressed air is taken from the compressed-air reservoir 40 via asecond controllable valve 44, and is expanded in a turbine 41 (or acompressed-air motor), in order to produce work. The turbine 41 drives agenerator 42 which produces three-phase electricity and—afterappropriate voltage and frequency matching—emits it to a local orsuperordinate grid system. When compressed air is stored and taken atthe same time, the compressed-air reservoir 40 is used, so to speak, asa “smoothing capacitor”.

The wind power installation 33 shown in FIG. 10 has an overall heightof, for example, 90 m, which is made up of 30 m for the mast 45 and 60 mfor the three rotors/cells 35 a, b, c, with a height of 20 m each. Amean wind speed of 5 m/s results in a power of 44 kW being produced,corresponding to 1056 kWh of energy per day. If the pressure reservoir40 has a storage volume of 5000 m³, 1250 kWh can be stored in it at apressure of 10 bar.

However, generators can also be arranged directly on the powertransmission 38 and produce electrical power directly when required,without the interposition of the compressed-air reservoir, thus allowingthe installation to be operated particularly flexibly, overall.

LIST OF REFERENCE SYMBOLS

10, 33 Wind power installation

11, 34 Axis (vertical)

12, 12′ Rotor

13, 14 Mounting plane

15, 15′ Rotor blade (lamellar)

16 Shaft

17 Generator unit

18 Pivoting axis (lamellar)

19, 31 Stop

20 Air flow (wind)

21 Limiting element

22, 23 Stop

24 Center area (reduced thickness)

25 Leading edge

26 Trailing edge

27 Circumferential circle

28 Spoked wheel

29, 30 End

32, 32′ Stop surface

35 Rotor

35 a, 35 b, 35 c Rotor

36 Guy

37 Frame

38 Power transmission

39 Compressor

40 Compressed-air reservoir (cavern)

41 Turbine

42 Generator

43, 44 Valve

45 Mast

A, . . . D Angle range

D1, D2 Diameter

d Thickness

b Width

R Radius (circumferential circle)

α, β, γ Angle

1. A wind power installation comprising: at least one rotor which canrotate about a vertical axis and, between two horizontal mountingplanes, which are located one above the other and separated, and aplurality of rotor blades, which are arranged distributed on acircumferential circle and can each pivot about a vertical pivotingaxis, and whose pivoting range is bounded at both ends by a stop,wherein the width of the rotor blades is less than approximately ⅓ ofthe radius of the circumferential circle.
 2. The wind power installationas claimed in claim 1, wherein twelve or more rotor blades are arrangedsuch that they can pivot on the circumferential circle of the rotor. 3.The wind power installation as claimed in claim 1, wherein the rotorblades are in the form of straight blades.
 4. The wind powerinstallation as claimed in claim 3, wherein the rotor blades each have aleading edge and a trailing edge, and have a reduced thickness betweenthe leading edge and the trailing edge.
 5. The wind power installationas claimed in claim 1, wherein the pivoting range of the rotor blades isin each case limited to an angle of about 100°-115°.
 6. The wind powerinstallation as claimed in claim 5, wherein, in one limit position ofthe pivoting range, the rotor blades each include an angle of about 50°with the radius vector of the circumferential circle which passesthrough the pivoting axis, and, in the other limit position of thepivoting range, include an angle of about 150°-165°.
 7. The wind powerinstallation as claimed in claim 4, wherein the pivoting axes of therotor blades are arranged within the rotor blades, in the vicinity of,but at a distance from, the leading edge.
 8. The wind power installationas claimed in claim 7, wherein the pivoting range of the rotor blades isin each case defined by a single stop which is arranged within thecircumferential circle.
 9. The wind power installation as claimed inclaim 4, wherein the pivoting axes of the rotor blades are arranged inthe leading edges of the rotor blades.
 10. The wind power installationas claimed in claim 9, wherein the pivoting range of the rotor blades isin each case defined by a limiting element which is in the form of acircular arc, concentrically surrounds the pivoting axis, and whose endseach form a stop.
 11. The wind power installation as claimed in claim 1,wherein the mounting planes are formed by spoked wheels which rotateabout the axis.
 12. The wind power installation as claimed in claim 1,wherein the wind power installation has a plurality of rotors which arearranged at different heights.
 13. The wind power installation asclaimed in claim 12, wherein the rotors are arranged one above the otherand rotate about the same axis.
 14. The wind power installation asclaimed in claim 13, wherein the rotors can rotate independently of oneanother.
 15. The wind power installation as claimed in claim 1, whereinthe rotor blades have an aerodynamic cross-sectional profile with apointed end and a round end.
 16. The wind power installation as claimedin claim 15, wherein the pivoting axes of the rotor blades are arrangedwithin the rotor blades in the vicinity of, but at a distance from, theround end, and wherein the pivoting range of the rotor blades is in eachcase defined by a single stop which is arranged within the rotor blade,rotationally fixed with respect to the pivoting axis.
 17. The wind powerinstallation as claimed in claim 1, wherein the rotor drives at leastone compressor via a power transmission, the compressor sucks in air onthe input side and is connected on the output side to a compressed-airreservoir, and wherein a turbine can be connected to the compressed-airreservoir and drives a generator in order to produce electricity. 18.The wind power installation as claimed in claim 17, wherein the rotorcan be selectively connected to a plurality of compressors via powertransmission.
 19. The wind power installation as claimed in claim 17,wherein the compressed-air reservoir is incorporated in the ground, andforms the foundation of the wind power installation arranged above it.20. The wind power installation as claimed in claim 15, wherein theaerodynamic cross-sectional profile is in the form of a stretcheddroplet.